Means for forming and dressing grinding wheels



June 6, 1944. JELLIS I 2,350,897

MEANS FOR FORMING AND DRESSING GRINDING WHEELS Filed p l 9, 1945 2 Sheets-Sheet 1 4' 4 w as A9 I f 16 2/ f7 2? 24 6' ZZZMI M. JELLIS June 6, 1944.

MEANS FOR FORMING AND DRESSING GRINDING WHEELS 2 Sheets-Sheet 2 Filed April 9, 1945 Patented June 6, 1944 MEANS FOR FORMING AND DRESSING WHEELS GRINDING Morgan Jellis, Peter-borough, Eng land, assignor to Coventry Gauge & Tool Companyfldmited.

Coventry, England Application April 9, 194:, Serial No. 482,454 In Great Britain August 14, 1942 1 Claim.

This invention relates to the forming and dressing of grinding wheels for use more particularly in producing gear teeth, thread-form and like profiles by means of a spirally ribbed grinding wheel profiled to the rack form of the desired pitch.

One of the reasons which has so far hindered the development of this method of producing r the kind and for the purposes herein referred to,

are formed and dressed to the required rach form by traversing a freely rotating annularly ribbed crushing roller of the correct form across the operative face of the rotating grinding wheel at a speed which is correlated with the rotationa speed of the said grinding wheel.

The traversing motion of the crushing roller is preferably produced by means of a cam of appropriate form driven through change gears from the spindle of the grinding wheel, or by other mechanical means, such as a screw and nut.

In the accompanying drawings,

Figures 1, 2 and 3 are views in side elevation. plan and front elevation respectively of a wheel forming and dressing apparatus embodying the present invention.

Figure 4 is a sectional plan view on the line A--A of Figure 3 illustrating one way of adjusting the crushing roller to the required helix angle of the spiral ribs on the grinding wheel.

Figure 5 is a detail view of the cam for traversing the'crushing roller.

' Figure 6 illustrates the developed form of the cam profile.

Referring to the embodiment of the invention illustrated in the accompanying drawings, 2 represents the crushing roller, 3 a head, and 4 the grinding wheel, said head and wheel being slidably and rotatably mounted respectively in a supporting structure 5.

The crushing roller 2 is formed with a plurality of annular ribs 2" and is arranged to have a traversing motion across and in contact with theperiphery of the grinding wheel I at a speed which is so correlated with the rotational speed of the grinding wheel as to form the said periphcry with helical ribs 4" having the required rack form.

For thispurpose the head 3 is attached to or formed in one piece with a member 6 which is free to slide in the upper part of the supporting structure 5 in a direction parallel with the rotational axis of the grinding wheel 4. The said head is moved in one direction with the roller in contact with the grinding wheel by means of a cam which is shown separately in Figure 5 and in its developed form in Figure 6. At the end of the traversing movement the roller is automatically disengaged from the grinding wheel in the manner hereinafter described and the head given a quick return motion under the influence of a spring 8 arranged in tension between studs 9 on the member 8 and on the supporting structure 5 respectively, the cam profile being suitably formed at I for that purpose.

The cam, which is rotatably mounted on a stub shaft it carried by the structure 5 and has its profile in constant contact with a stylus II on the member 6, as seen in Figures 1 and 2, is driven from the, spindle l2 of the grinding wheel at the requisite speed by means of a change gear II. The grinding wheel spindle itself can be driven in any suitable manner as by means of a belt II, and pulley II.

In order to provide for the movement of the crushing roller 2 into and out of contact with the grinding wheel 4, the said roller is rotatably mounted in a cylindrical member it which is free to slide in the head 3, the latter being formed with a tubular bore for that purpose. The said member I6 is carried by the screw-threaded end of a spindle H which is free to turn but not to move axially in the upper part of the head. For feed purposes the upper end of the spindle is fitted with a hand wheel l8 whereby the spindle l'l canbe rotated to cause the cylindrical member l6, and hence the crushing roller carried thereby, to be moved towards and away from the grinding wheel.

The operation of the wheel forming apparatus I is entirely automatic, the movement of the crushing roller into and out of contact with the grinding wheel at the commencement and end of its working traverse being controlled by means of inclined surfaces I 9 on a bar 20 co-acting with similar inclined surfaces 2| on a collar 22 fixed to the spindle H. The said bar which is freely slidable in a projection 24 on the structure 5 and .a push fit in a'lug 3 on the head 3, is fitted with adjustable stops 23; 23' arranged fore and aft of the projection 24. The arrangement is such that during the traversing motion of the head under the action of the cam the bar moves with the head. The stop 23 is adjusted on the bar so an immediately prior to the head reaching theendofitsworkingstrokethe said stop comes into contact with the back of the projection 2| thereby arresting further forward movement ofthebarandcausingtheinclinedsurfaces It thereon to co-operate with theinclined surfaces it on the collar 22 to lift the spindle l1 and member llandhencetoraisethecmshingrollerclear of the grinding wheel. The other stop 23" is ad- Justed on the bar so that immediately prior to the end of the quick return motion of the head under the influence of the spring I, the said stop 23' makes contact with the front face of the projection 14 thereby arrestingthe return movement of the bar and causing the aforesaid cooperating inclined surfaces to depress the crushing roller into engagement with the grinding,

wheel for the next forward traverse or working stroke. a

To provide for angular adjustment of the crushing roller according to the helix angle of the ribs required on the grinding wheel, as represented in Figure 4, the reduced upper part It of the cylindrical member aforesaid has a sliding keyedconnection with a worm wheel 26 which is rotatably mounted in the head and is engaged by a worm l'lalso rotatahly mounted in the head. The worm is turned to give the required adjustment by means of an outside knob 28.

In order to facilitate the crush-forming operation the annular ribs 2- on the crushing roller may .be of progressively increasing diameter and/or width from the leading end, the core diameter being uniform'and the rib or ribs at the trailing end of full form. Alternatively, a tapered full form roller may be employed.

' I claim:

Apparatus for forming and dressing grinding wheels of the kind and for the p rposes described comprising a supporting structure carrying the grinding wheel, a head slidably mounted in said structure, an annularly ribbed crushing roller freely rotatable in said head; a cam acting on said head for traversing the crushing roller across and in contac with the operative face of said grinding why at a speed correlated with the rota'tional speed of the latter, and means whereby the crushing roller is automatically moved into and out of engagement with the grinding wheel at the commencement and termination respectively of its traversing motion.

MORGAN JELLIS. 

